First off, I am not assuming all the cars are headed downtown. Secondly, when I speak of motorists that have the option of using transit on Sheppard over the 401 I am talking about those who start/end their trips on Sheppard and are generally travelling within the city. I am not speaking about those who are just passing through the area on the 401.
My overall point that I'm trying to make is that higher order transit whether it is subway, LRT or BRT makes more sense on Sheppard East versus Finch East. It supports the city's planning objectives and extends an already existing rapid transit line even if it means a transfer has to be made between the two. Why would you want to build an LRT that parallels a subway line 2km to the south?

Sure, the new population traveling to/from points along Sheppard will have the option of driving and using the 401. However, the 401 is a very slow drive at peak times, and even weekends at certain points between Yonge and McCowan. The 401 westbound is jammed from Morningside as early as 6:30am to well past 9am. Using Sheppard westbound in the morning is just as fast, or even faster than using the 401. If these motorists are given the option of higher order transit along Sheppard, I'm sure some would use it over being stuck on the 401.

The city's Official Plan lists Sheppard East from Yonge to McCowan as an "Avenue". An "Avenue" are streets the city wants to redevelop to be lined with mid rise buildings that blend with the existing neighbourhoods and can used for new residential and commercial uses. The majority of these "Avenues" are currently located on existing or future/propsed rapid transit routes (parts of Yonge St., Bloor/Danforth, Eglinton, Kingston Rd, etc.) as the increased development needs to be serviced by better transit than just buses in mixed traffic. Finch East is not an "Avenue" as there is very little land that can be redeveloped to make it one.
Redeveloping Sheppard East will increase ridership a lot, well over what Finch East ridership is now, since it will be lined with mixed used buildings compared to Finch which is mostly residential. Ridership on 39/199 is at roughly 42,000 compared to 85/190 at roughly 37,000. Essentially, it makes more sense to implement higher order transit on Sheppard East than on Finch East. I personally think if they are going to implement bus lanes on Sheppard they need to go from Don Mills to at the very least Markham Rd.

The TTC and City have identified that if no LRT (or subway) is built on Sheppard East that they want bus only lanes implemented. It doesn't have to be Highway 7 style BRT, I'm sure lanes similar to Allen Rd/Dufferin St between Sheppard West Station & the York U busway would be just fine.

I believe the only streetcar route that has a "Flexity style" layout with the route name and destination on the bus destination signs is 509. This was done part way through the 509 replacement bus service during the Queens Quay reconstruction. I can't remember the reason behind it though at the moment.

Some 192 late evening runs do go onto 300A. They do a round trip and deadhead back to Queensway from Pearson if I'm not wrong. Maybe this bus was way off schedule and was told to deadhead back from Danforth & Warden. Gardiner-Lake Shore-Woodbine-Danforth Ave is the usual deadheading route between Queensway and Danforth & Warden.

It's called Roe Loop and it hasn't been used for regular service since the 61 Roe Loop branch was eliminated and all 61 service was extended to Highway 401 at all times back in 2004. The odd 61 and 142 short turn use it these days, there is even a short turn sign for them to use indicating they turn around at Roe Loop.
Can someone remind me now, back in the early/mid 2000s did Eglitnon (Comstock) operate 61 at all times or was it only during the weekend evening interline with 51?

7666 was involved in this accident on Eglinton back in 2013: Witnesses sought after woman hit by TTC bus in Scarborough
The woman eventually passed away. The family sued the TTC after the accident. The family of the teen killed in the accident involving then 7794 (now 7882) also sued the TTC. The renumbering of the buses must be part of the settlement the TTC offered in these cases.
The renumbering of 7666 must have been fairly recent. I spotted it in service within the last two weeks.